88 ' The Ohio Journal of Science [Vol. XVII, No. 3, 



geology proceeds, and the paleogeographic maps grow, and 

 multiply, and the columnar section becomes more complete, 

 until such a time as he can have a complete series of forms from 

 the beginning to the present. Then he may be able to answer 

 the great question whether each flora and fauna has developed 

 from a previous ensemble of life by gradual transitional changes, 

 or has arisen by a sudden large change, or a creative fiat at 

 some critical moment. Since this work of a biologic nature 

 cannot precede, but must follow the stratigraphic and paleo- 

 geographic work it means many more years and probably 

 centuries before the geologist need lay down his hammer and 

 spade. 



If there are enchainments, to use Gaudry's term, between 

 species of one period and those of the next, our field studies 

 ought to find them. V^ery few have yet been found, but in most 

 cases there is rather a biologic hiatus. I have faith to believe 

 that within the next thousand years or so a considerable number 

 of real enchainments will be established. We may also find 

 many actual centers of dispersion where the evolution of a 

 fauna has gone rapidly forward in a more or less restricted area 

 and from which the new forms have spread in startling sudden- 

 ness and profusion. Indeed it is possible as we push our 

 research farther and farther back and finally have mapped and 

 studied minutely all stratified rocks from all parts of the earth 

 that we shall find the beginnings of many of our large types of 

 life. We may even find substantial paleontologic evidence for 

 the evolution of man from the lower, more primitive and 

 generalized mammals. 



A few figures will present the biologic possibilities in a very 

 different way. Pratt in 1911, estimated the described forms 

 of animals to be a little over a half million. A recent estimate 

 of the number of fossil animal species described gives 100,000. 

 The 500,000 living forms were taken from one geologic period 

 at one time. The 100,000 fossil forms were taken from the 

 whole geologic section, which undoubtedly includes hundreds of 

 geologic "times," any one of which w^as as long as the present, 

 had as distinct a fauna as the present, and perhaps as many 

 species with hard or preservable parts as we have now. Of 

 course, our recent 500,000 described forms does not include 

 nearly all of the living forms, possibly not 20%, and this 

 ratio may be similar to the ratio of animals with hard parts 



